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What is the meaning of the terms 2P2d, 3P3d, 4P3d, 4P4d, 4P3d+N/2 and 4P3d+OSN on the Compact NSX circuit-breaker trip units.

The first number corresponds to the number of poles.
The second number corresponds to the number of protected poles.
The first letter stands for Pole.
The second letter stands for trip unit ("déclencheur" in French).

Examples:
4P3d is a 4-pole trip unit with 3 protected poles (not the neutral).
4P3d+N/2 is a 4-pole trip unit with 3 protected poles and the neutral at half rating due to the neutral cable being half the phase cable cross sectional area.
4P3d+OSN is a 4-pole trip unit with 3 protected poles and with oversized protection of the neutral (Over Size Neutral).